The utilization of renewable energy sources is becoming popular as a way to reduce the dependence on fossil fuels and to decrease the emissions of pollutants and green-house gases into the atmosphere. Solar thermal systems provide the capability of generating heat, electric power, and/or cooling in a sustainable way and for a variety of applications due to the relatively large range of temperatures that different collector configurations can provide. Readily available in the market, solar collectors vary in performance depending on their design. The effective transfer of the heat obtained from the sun to the heat-transfer fluid remains a subject of continued research.